The present invention generally relates to an examining apparatus, and more particularly, to a soldering appearance inspection apparatus for automatically examining whether or not lead wires are properly soldered onto soldering portions of a printed circuit board or the like.
Recently, there have been proposed various kinds of soldering appearance inspection apparatuses for the purpose as described above. The conventional inspection apparatus for discriminating good products by obtaining a three-dimensional shape of a soldered portion by a light ray cutting system as disclosed, for example, in Japanese Patent Laid-Open Publication Tokkaisho No. 63-196980, has been so arranged to effect the judgement by comparing a histogram in dark/light image of the solder and its binary coded image over a predetermined threshold value, with those of a good product. However, the above known arrangement requires a long processing time, while a photo-detector having a large dynamic range as referred to therein is necessary, and thus, this apparatus is not suitable for practical applications. There has also been conventionally proposed in Japanese Patent Laid-Open Publication Tokkaisho No. 64-68606, an inspection apparatus for judging a quality of soldering through utilization of the fact that, upon projection of a concentric multi-circular pattern light onto a soldered portion, the multi-circular pattern image is distorted when the configuration of the soldered portion is abnormal. Another known apparatus disclosed, for example, in Japanese Patent Laid-Open Publication Tokkaisho No. 64-73207 is so arranged that by once projecting ring-shaped pattern light onto a printed circuit board, a judgement is made as to whether or not the solder configuration is good by a distance between a high brightness portion formed by reflection of its indirect light on a soldered face and a lead wire.
However, in the conventional soldering appearance inspection apparatuses as referred to above, although the solder configurations may be compared with those on a good printed circuit board in the case where scattering in the sizes and positions of soldered portions and lead wires to be examined is small, it has been difficult to inspect soldering appearance of a printed circuit board in which positions and sizes of soldered portion are scattered or lead wires are merely soldered onto land portions without the presence of any through-holes.
Similarly, it has also been difficult to detect a faulty state such as scorching or no luster on the surfaces of the soldered portions by the partial pattern light projecting method.